Transmission and brake control system



A (uw Feb. 3, 1959 w. B. HERNDON ET AL 2,872,000

TRANSMISSION ANO BRAKE CONTROL SYSTEM Filed may 13, 1953 J ATTORNEY i Iv l United States O i."

TRANSMISSION ANDBRAKE CoN'rRoL sYsrEM Application May 13, 1953, SerialNo. 354,832

6 Claims. (c1. 19a-4) This invention relates to transmission controlsystems and more particularly to a transmission control system for avehicle adapted to provide for change of drive ratio in the transmissionwhen the vehicle brake is applied. More particularly, it is an object ofthis invention to provide in a plural ratio automatically controlledvehicle transmission, means automatically operative without anyattention on the part of the vehicle operator to downshift thetransmission drive ratio when the vehicle is being braked. Thisautomatic downshift of the transmission is of advantage as an assist invehicle braking since it automatically provides for increased enginebraking when the operator depresses the brake pedal. Such engine brakingis of great value in assisting the vehicle brakes to stop the vehicle,particularly in hilly or mountainous country where the vehicle brakesmay be continuously applied for relatively long periods of time. Theautomatic downshift of the transmission provided by this control systemminimizes the braking effort which the vehicle brakes may be called uponto supply, thus reducing the time period during which 4the vehiclebrakes must be applied and preventing over-heating and fading of thevehicle brakes.

The control system of this invention incorporates a valve responsive tothe Vehicle master brake cylinder for admitting pump line pressure to ashift valve to position the transmission shift` valve to downshift thetransmission. The downshift controlled by the transmission shift valvemay be a downshift from over-drive to direct drive if desired, but inthe embodiment shown, the downshift provided by depressing the `vehiclebrake pedal is a downshift from direct drive to reduction drive in thetransmission.

The invention represents an improvement for automatically shiftabletransmissions of the type disclosed in the application of Walter B.Herndon, Serial Number 235,213, filed July 5, 1951. In view of the priordisclosure of a complete transmission control system to which thisinvention may be applied in the above identifed application for LettersPatent, the present invention is shown schematically in the single gure,being limited to a single pair of transmission servo'members adapted tobe selectively actuated to select a pair of transmission drive ratios.It will be understood, however, that the invention may be applied to anyof the transmission servo members of the said application for LettersPatent.

An object of this invention is to provide means responsive to movementof the vehicle brake pedal to a brake application position to cause adownshift of transmission drive rato to assist the vehicle brakes inslowing down a vehicle.

A further object of this invention is to provide automatically operablehydraulic means operative upon application of the vehicle brakes tocause a change of transmission drive ratio. l

Another object of this invention is to provide a valve member controlledby a vehicle brake master cylinder for providing automatic change oftransmission drive ratio upon application of the vehicle brakes.

2,872,000 ifteafed ZFeb. 3,.` 1959 'A further object of this inventionis to provide in a; transmission control system including a shift valvenormally controlled as a function of vehicle speed and engine torquedemand, an overriding control between the vehicle brake applying meansand the transmission drive ratio control system for causing atransmission downshift upon application of the vehicle brakes.

The above recited advantages and other features and objects of thisinvention will be apparent from the following description and claims,taken in conjunction with the following drawing, in which:

The figure shows a schematic diagram of a control system for atransmission embodying the features of this invention.

Referring to the diagram, there is shown a pair of fluid pressureactuated servo units consisting of a band servo 10 and a clutch servo20. When the band servo 10 is energized to apply a band (not shown) to adrum (not shown) one element of a planetary gearing unit is braked toprovide a reaction member for reduction drive through planetary gearing.Band servo 10 may brake a planetary sun gear for reduction drive. Whenthe clutch servo 20 is energized, clutch plates 22 and 23 are engaged toclutch a pair of elements of a planetary gearing unit to each other fordirect drive through the planetary gearing unit. Clutch servo 20 maylock a sun gear to a ring gear for direct drive. The gearing and servosare vfully described in the application for Letters Patent Serial No.235,213, filed July 5, 1951.

The control system of the present invention includes a pump 30, amanually operable valve 31, a shift valve 80, a valve 60 controlled bythe vehicle accelerator pedal, and a valve controlled by the vehiclebrake master cylinder 103. Pump 30 may be engine driven and anadditional pump (not shown) driven in response to vehicle speed as bythe vehicle tail shaft (not shown) may be provided if desired.

The reduction drive servo 10 is composed of a stem 11 adapted to apply aband (not shown) for establishing reduction drive when the stem 11 isforced outwardly from the casing 12. A piston 13 at the base`0f stern 11separates a chamber 14 from chamber 15. Stem 11 is provided with apassage 16 to hydraulically connect a chamber 15 with a chamber 17. Aspring 25 tends to move stem 11 to release the band (not shown). Apiston 19 is xed to stem 11.

The direct drive clutch servo 20 for establishing direct drive throughthe planetary gearing unit consists of a piston 21 adapted to engageclutch plates 22 and 23 when fluid pressure is admitted to a chamber 24.A spring 26 releases the clutch plates when pressure is exhausted fromchamber 24.

Pump line pressure from pump 30 is conducted to port 32 of a manuallyoperable valve 31 and to a governor 102 through a passage 120. In thedrive position of valve 31 as illustrated in the gure, line pressurefrom passage is admitted to'chamber 14 of p servo 10 through ports 32and 33 o'f'valve'31 and passage 121. In reduction drive, chambers 15 and17 of servo 10 are connectedto exhaust through a passage 123 and ports98 and 99 ofa shift valve 80. Pressure in chamber 14 is then effectiveto move stem 11 outwardly from casing 12 for establishing reductiondrive.

A pressure metering valve 55 is provided with a valve body 56 composedof lands 57, 58 and 59 and a plunger valve member 60 composed of lands61 and 62 and a stem 63. A spring 64 is interposed between one end of Yvalve 55 and the adjacent end of plunger valve 60. Stem l 63 is forcedinwardly against spring 64 byk a cam 65 operated by the vehicleaccelerator pedalv(not shown) as the accelerator pedal -iskmoved tosupply-an increasing quantity of gasoline to the vehicle engine. Casing54 is supplied with ports 66, 67, 68, 69, and 71, al1 associated withvalve 55. Casing 54 is also provided with ports 72, 73 and 74 associatedwith plunger valve 60. Port 66 admits pump line pressure from manuallyoperable valve 31 to a chamber between lands 58 and 59. Port 67 is apressure delivery port for admitting pressure to passage 1241. Ports 68and 69 connect passage 124 to the valve bore. Port 70 exhausts to thetransmission sump, and port 71 admits pressure from passage 124 to achamber at one end of a detent plug 76. lt will be noted that thediameter of land 58 is greater than that of land 57. Pressure deliveredto passage 124 reacts upon land 58, tending to move the valve 55 againstspring 64 to cut off the admission of fluid to passage 124. Detent plug76 provides a yieldable resistance which the vehicle driver can feel inpressing the accelerator pedal to its forced downshift position, butwhich is not felt during normal movement of the accelerator pedal. Asstem 63 is moved into the casing against spring 64, the pressure levelof fluid pressure in passage 124 increases. Port 72 admits pump linepressure to the valve bore adjacent land 61. Port 73 connects to apassage 125 and port 74 exhausts to the transmission sump.

A shift valve in a casing S1 is adapted to be moved from a reductiondrive position to a direct drive position for selecting direct drive.Casing 81 is drilled for a shuttle member 82, for a piston 83, valvemember 80, and a governor plug 86. Casing 81 is provided with ports 87,8S, 89 and 90. Port 87 connects to passage 124 to admit variablepressure from valve 55 to a chamber 91a. Ports 88 and 90 are connectedby a passage 91 to admit pressure from chamber 91a to a chamber 92. Port89 connects to a passage 126. A pair of springs 93 and 94 tend to biasthe valve member 80 to its downshift or reduction drive position. Astern 95 carried by piston 83 contacts shuttle stem 82 when pressure isadmitted to chamber 91a. Valve member 80 is composed of a pair of lands84 and 85 and is provided with a stem 96 adapted to contact a governorplug 86. Port 97 connects to a line pressure supply passage 122. Port 9Sconnects to a passage 123. Ports 99 and 100 exhaust to the transmissionsump, and port 101 connects to a governor pressure delivery passage 128.PreS- sure in passage 128 is delivered thereto by a governor (shownschematically at 102) adapted to deliver a variable pressure whichincreases with increase in vehicle speed. A governor of the type whichmay be employed is shown in Figure 5 of the patent to Earl A. Thompson,2,204,872, issued June 18, 1940. The governor may be driven by thevehicle drive shaft so as to be responsive to vehicle speed.

Shift valve 80 is illustrated in its downshift position wherein passage123 leading to band servo 10 and clutch servo 20 is connected to exhaustport 99 through port 98. 1n its upshift position valve 80 connectspassage 122 to passage 123 by Way of ports 97 and 98 to admit linepressure to passage 123 to release the reduction drive servo and actuatethe direct drive clutch.

Further referring to the figure, there is schematically shown aconventional vehicle brake master cylinder 103 of the type adapted todeliver fluid pressure to the Vehicle brakes for brake application whenthe vehicle brake pedal is depressed. When the brake pedal (not shown)is depressed to apply the vehicle brakes, master cylinder 103 deliversHuid under pressure to passage 127. When the brake pedal is released,uid in passage 127 is drawn back through passage 127 into the mastercylinder.

An additional valve member 105 composed of lands 106 and 107 isinitially spring biased by a spring 108 to connect passage 125 topassage 126, both passages 125 and 126 being normally connected toexhaust through ports 73 and 74 of plunger valve 60. Plunger 60 ismovable through a first range of movement for causing valve 55 todeliver a variable pressure to passage 124 while maintaining passage 125connected to exhaust port 74 through port 73. When, however, theaccelerator pedal is fully depressed, plunger 60 connects passage 125 toline pressure through ports 72 and 73 to provide an accelerator pedalcontrolled forced downshift. A diaphragm 109 separates one end of land106 from the adjacent end of a plunger 110 movable in response topressure which may be admitted to a chamber 111 to move valve 105against spring 108. A chamber 112 is connected by a passage 113 to thesump of the master cylinder 103 to prevent any fluid trap that otherwisemight develop due to leakage of fluid from chamber 111 past plunger 110.Port 114 connects a chamber 115 to the transmission sump to prevent anyuid block due to leakage of fluid past land 106 of valve 105. Port 116connects to passage leading to port 73 of plunger valve 60. Port 117admits vpump line pressure from line pressure supply passage 122 to thevalve bore. Port 118 connects to delivery passage 126 leading to port 89of shift valve 80.

Operation When the manually operable valve 31 is moved one notch to theleft from the position shown, pressure in passage 121 and chamber 14 ofservo 10 is exhausted through ports 33 and 34 of the manually operablevalve to release the reduction drive servo 10. The clutch servo 20 isexhausted through passage 123 and ports 98 and 99 of shift valve 80.With both the band servo and clutch servo released, the transmission isin neutral.

With the manually operable valve positioned for forward drive asillustrated, pump line pressure is admitted to chamber 14 of servo 10 byway of passages 120 and 121 to establish reduction drive. Upon vehicleacceleration, governor pressure in chamber 104 beneath governor plug 86acting upon governor plug 86 builds up until at some vehicle speed theshift valve is moved to its upshift or direct drive position. 1n theupshift position of valve S0, line pressure is admitted from passage 122to passage 123 through ports 97 and 98 of valve 80. Pressure in passage123 is supplied to clutch servo chamber 24 to apply the direct driveclutch and is also supplied to chambers 15 and 17 of servo 10 to releasethe reduction drive servo 10. This pressure in chambers 15 and 17 andthe force of spring 25 will release the reduction drive servo eventhough pressure is simultaneously being supplied to chamber 14 of servo10 by way of ports 32 and 33 of valve 31 and passage 121.

In normal operation, the timing of the shift of shift valve 80 is afunction of vehicle speed and engine torque demand. Valve 55 delivers avariable pressure which increases with increase of engine throttleopening to passage 124 to one end of pin 82 and through passage 91 tochamber 92 of piston 83, tending to downshift the valve. Governorpressure, acting upon governor plug 86 tends to upshift the valve. Whenthe accelerator pedal is fully depressed, line pressure is admitted topassage 125 by Way of ports 72 and 73 of plunger valve 66. This linepressure is conducted to chamber 92 by way of ports 116 and 11S of valve105, passage 126, and port 89. Unless the vehicle speed be excessive,line pressure ir: chamber 92 will ybe effective to overcome the effectof governor pressure in chamber 104 to -downshift the shift valve forforced downshift to reduction drive. This forced downshift isparticularly useful for rapid acceleration in passing other vehicles.

In order to provide additional braking force to assist the vehiclebrakes in stopping the vehicle, the valve 105, controlled by the brakesystem master cylinder 103 is prov-ided. Upon application of the vehiclewheel brakes, the master cylinder 103 delivers fluid under pressure topassage 127 and chamber 111 adjacent one end of plunger 110. Thispressure is effective to move valve body 105 against spring 10S to cutolf passage 125 and to connect ports 117 and 118. Line pressure isthereupon admitted from passage 122 to passage 126 and to chamber 92 ofshift valve 80, causing a forced downshift of transmission drive ratio.This downshift of transmission drive ratio provides increased enginebraking acting to assist the vehicle brakes in slowing down the vehicle.is particularly useful in descending long grades Where continuous brakeapplication is necessary and in assisting in the rapid deceleration ofthe vehicle. At high vehicle speeds, and after prolonged continuous use,it is known that lbrakes have a tendency to fade and to overheat. Thisarrangement is of assistance in overcoming these braking problems. Assoon as the vehicle brake pedal is released, oil in passage 127 is drawnback into the master cylinder, permitting spring 108 to move valve 105back to its normal operation position. Oil pressure in passage 126 willthereupon be exhausted through passage 125 and ports 73 and 74 of theplunger valve 60 to permit normal control of the shift valve 8,0.

There has thus been provided an automatically operable means controlledby the vehicle brake pedal for causing transmission downshift uponapplication of the vehicle brakes. While the particular embodimentdescribed consists of a hydraulic control, it will be understood thatother control means responsive to the application of the vehicle brakesmight be employed.

We claim:

l. ln a control system for a vehicle transmission having a plurality ofuid pressure responsive servo members operable to establish a pluralityof transmission drive ratios, a iluid pressure source, a shift valve forcontrolling the admission of uid pressure to said servo members toselect the transmission ydrive ratio, vehicle speed responsive mechanismfor applying force to move said valve to select one transmission driveratio, vehicle brake controlling means, and valve means controlled bysaid vehicle brake controlling means effective to direct fluid pressureto said shift valve for moving said shift valve to select a secondtransmission drive ratio when said vehicle brakes are applied.

2. In a control system for a vehicle transmission having a plurality offluid pressure responsive servo members operable to establish aplurality of transmission drive ratios, a fluid pressure source, a shiftvalve for controlling the .admission of fluid pressure to said servomembers to select the transmission drive ratio, means for positioningsaid shift valve to select one transmission drive ratio, means forapplying the Vehicle brakes, an additional valve controlled by saidbrake applying means connected to said fluid pressure source, a passageconecting said additional valve to said shift valve, and means yieldablybiasing said additional valve to connect said passage to exhaust, saidadditional valve being movable in response to actuation of said brakeapplying means to apply the vehicle brakes to connect said passage tosaid uid pressure source for moving said shift valve to select a secondtransmission drive ratio.

3. In a control system for a vehicle transmission having a plurality ofuid pressure responsive servo members operable to establish a pluralityof transmission drive ratios, a uid pressure source, a shift valve forcontrolling the admission of fluid pressure to said servo members toselect the transmission drive ratio, vehicle speed responsive mechanismfor positioning said shift valve to select one transmission drive ratio,a brake valve, a passage connecting said brake valve to said shiftvalve, a manually operable plunger hydraulically connected to said brakevalve, a hydraulic connection from said fluid pressure source to saidbrake valve, an exhaust port associated with said plunger, meansnormally biasing said brake valve to connect said passage to saidexhaust port, means for applying said vehicle brakes, and meansresponsive to said means for applying said vehicle brakes forpositioning said brake valve to connect said passage to said fluidpressure source for moving said shift valve to select anothertransmission drive ratio.

This feature 4. In a control system for a vehicle transmission having aplurality of iluid pressure responsive servo members operable toestablish a plurality of transmission drive ratios, a iiuid pressuresource, a shift valve for controlling the admission of iluid pressure tosaid servo members to select the transmission drive ratio, means forpositioning said shift valve to select one drive ratio, a mastercylinder for applying the vehicle brakes, an additional valve controlledby said master cylinder connected to said fluid pressure source, apassage connecting said additional valve to said shift valve, and meansyieldably biasing said additional valve to connect said passage toexhaust, said master cylinder being effective to position saidadditional valve to connect said passage to said lluid pressure sourcefor positioning said shift valve to select a second transmission driveratio when said vehicle brakes are applied.

5. In a control system for a vehicle transmission having a plurality offluid pressure responsive servo members operable to establish aplurality of transmission drive ratios, a uid pressure source, a shiftvalve for controlling the admission of fluid pressure to said servomembers to select the transmission drive ratio, means for positioningsaid shift valve to select one transmission drive ratio, a mastercylinder for applying the vehicle brakes, an additional valve controlledby said master cylinder connected to said fluid pressure source, apassage connecting said additional valve to said shift valve, a manuallyoperable plunger connected to said fluid pressure source and to saidadditional valve, an exhaust port associated with said plunger, andmeans yieldably biasing said additional valve to normally connect saidpassage to said plunger through said additional valve, said plungerbeing movable through a first range of movement wherein said passage isconnected to said exhaust port and movable to a second position forconnecting said passage to said fluid pressure source through saidadditional valve for positioning said shift valve to select a secondtransmission drive ratio.

6. In a control system for a vehicle transmission having a plurality ofuid pressure responsive servo members operable to establish a pluralityof transmission drive ratios, a uid pressure source, a shift valve forcontrolling the admission of iluid pressure to said servo members toselect the transmission drive ratio, vehicle speed responsive means forpositioning said shift valve tov select one transmission drive ratio, amaster cylinder for applying the vehicle brakes, an additional valvecontrolled by said master cylinder connected to said fluid pressuresource, a passage connecting said additional valve to said shift valve,a manually operable plunger connected to said uid pressure source and tosaid additional valve, an exhaust port associated with said plunger,means yieldably biasing said additional valve to normally connect saidpassage to said plunger through said additional valve, said plungerbeing movable through a first range of movement wherein said passage isconnected to exhaust and movable to a second position to direct fluidpressure to said passage through said additional valve, said additionalvalve being movable responsive to fluid pressure delivered by saidmaster cylinder to connect said passage to said iiuid pressure sourcefor establishing a second transmission drive ratio irrespective of theposition of said plunger when said master cyl-v inder is actuated toapply the vehicle brakes.

References Cited in the tile of this patent UNITED STATES PATENTS1,910,180 Poncelot May 23, 1933 `1,980,797 vHale Nov. 13, 1934 1,980,798Hale Nov. 13, 1934 2,103,540 Livermore Dec. 28, 1937 2,186,334 Hale Jan.9, 1940 2,263,707 Strige Nov. 25, 1941 2,299,475 Farmer Oct. 20, 19422,349,350 Iandasek May 23, 1944 2,408,008 Tipton Sept. 24, 1946

